Flagstaff & Anemometers

A flagstaff is a spar used exclusively for displaying the national flag at the stern of a ship. The flagpole, flagmast, flagstaff, or staff can be a simple support made of wood or metal. The pole is usually topped by a flat plate or ball called a "truck".
An anemometer is a device used for measuring wind speed. The cup anemometer has a vertical axis and three angled cups that capture the wind. The cups turn because the shape is such that the resistance to flow is asymmetric about each cup.